Building of a section of the sticky spiral in Araneus diadematus

This video clip shows in slow motion how an adult cross spider Araneus diadematus builds a section of the sticky spiral.

Among other things, this film depicts nicely that the sticky thread actually consists of two threads, produced by separate spinnerets. These two threads combine and merge shortly after leaving the spinnerets. It is not certain, which forces act on the threads causing them to merge. Possibly, it is the surface tension of the glue, which is produced by other glands of the spider and applied to the sticky thread as it is being produced.

This film also shows how the spiders plucks the newly laid sticky silk. The function of this plucking is is not certain. It is assumed, that it promotes the formation of the sticky droplets, which are, however, not fully formed until at least 20 seconds later (cf. movie on sticky spiral construction).